Anorexia Nervosa (AN) affects 0.5-1% of college-aged women in the US and is characterized by extreme, self- induced starvation. Of the many medical co-morbidities associated with AN, severe bone loss is the most common and often persists despite weight recovery. This bone loss is significant because women with AN also have an increased fracture risk; a prospective study demonstrated that women with AN have a 7-fold increased risk of fractures as compared to age-matched controls. Therefore, a treatment to prevent the severe bone loss associated with AN is critical. There are currently no approved treatments for AN-associated bone loss. Therapies which prevent bone loss in normal-weight, hypogonadal women, such as estrogen, do not improve bone mineral density in women with AN. This is likely because the pathogenesis of bone loss due to nutritional deprivation differs from that of post-menopausal osteoporosis. In AN, there is a dramatic decrease in bone formation. Therefore an agent which stimulates bone formation would be an important potential treatment. Currently teriparatide (PTH) is the only anabolic agent approved by the FDA for the treatment of osteoporosis. As the effects of PTH on bone are known to be mediated through IGF-I and IGF-I levels are low in states of nutritional deficiency, we propose to investigate the effects of PTH on bone mass in women with AN. We will randomize thirty women with AN to treatment with either PTH or placebo and follow them prospectively for 6 months. We will measure bone mineral density, parameters of bone microarchitecture and bone strength at baseline and at 6 months. We will also measure markers of bone formation and resorption, IGF-I and sclerostin levels at baseline and monthly during the course of the study. Dr. Fazeli is an Instructor in Medicine at Harvard Medical School and Assistant in Medicine at Massachusetts General Hospital (MGH). She is on staff in the Neuroendocrine Unit at MGH and devotes the majority of her time to clinical research. Her expertise in studying hormonal abnormalities in AN positions her to lead the proposed project. She is well-supported by MGH and has full access to the Neuroendocrine Unit, Clinical Research Center and Harvard Catalyst CTSC resources. Her co-mentors, Drs. Anne Klibanski and Mary Bouxsein, are well-funded and invested in the direction of Dr. Fazeli's research. During the award period, Dr. Fazeli will obtain critical trainig in biostatistics and research design at the Harvard School of Public Health, where she is currently a Master of Public Health student, as well as important skills in novel investigational methods of determining bone strength. If awarded, this grant will support Dr. Fazeli's training in clinical research, with the ultimate goal of becoming an independent investigator with an expertise in combining neuroendocrinology and bone biology to better understand the pathophysiology of bone loss in disorders of under-nutrition.